Diesel engines have become increasingly popular for operating motor vehicles. Although this type of engine provides increased fuel economy over the more traditional gasoline engines, diesel engines are particularly sensitive to contaminates in the fuel oil supply, particularly water mixed with the fuel oil. Water mixed with fuel oil has many deleterious effects on the vehicle engine, and should be separated out for the proper operation of the diesel engine. A filter may be provided downstream (on the pressure side) of a fuel pump to protect downstream components.
Heretofore, filters have used internal support frames with or without coalescer elements to promote coalescence of water droplets that will flow down the internal support frame or drop by gravity to the bottom of the filter where they can be collected, for example, in a collection bowl. While this removes a significant portion of the water from the fuel, some water droplets may become re-entrained in the fuel and thus pass out of the filter with the fuel, particularly when the filter is located on the pressure side of the fuel pump. In the past, secondary coalescing elements have been provided within the interior of the internal support frame to capture these remaining or re-entrained water droplets. These secondary coalescing elements have included an annulus of hydrophobic material. This, however, adds considerable cost given that hydrophobic material is relatively expensive.